Can I exclude specific IPs so I can test the plugin on my various stores?

It's not possible to exclude specific IPs from being picked up, but there are some good ways to test it out in any case.

A couple of suggestions:1) Use a VPN such as Astrill, details are here: https://shopifyninjas.zendesk.com/entries/98186047-How-can-I-test-that-the-IP-Redirect-Plugin-is-working-

2) Or, the easy way is, if you go into your store inside Theme Settings, you won't get redirected, regardless of your IP. So for example, if you were setting up a site for Australia but you are in the US -- if you visit the AU site from a US IP on the front-end, you might get redirected if you enter that way. So what you can do instead is, go into your Australian store from the Admin > Themes > Customise Theme. That way you can see & test as needed, without being redirected.